In the practice of dentistry, it is often necessary for a dentist to perform dental procedures at various orientations relative to the dental work. This typically requires the dentist to have a variety of dental instruments at their disposal, each having at one or both ends a fixed tool with a tip having a given shape and orientation. Alternatively, the dentist can use a dental instrument comprising an instrument body that accepts a tool having a tip. The tool can be adjusted so the tip can take on a variety of orientations (i.e., positions) relative to the instrument body. In addition, with some instruments, the tool may be replaced with another tool having a different tip configuration. For such adjustable dental instruments, it is important that the tool be capable of being rapidly adjusted to a particular orientation and then fixed tightly in place within the instrument body. It is also important that the instrument body and tool be amenable to being rapidly cleaned for subsequent re-use.
As an example of such an instrument, U.S. Pat. No. 649,234 discloses a dental tool with a tool having a ball-end disposed in a concave socket screwed into one end of the instrument. The socket has an aperture with recesses through which the instrument tip extends. The ball-end is held in place within the concave socket by tightening a threaded rod running along the axis of the instrument handle which pushes the ball-end into the socket. While the orientation of the instrument tip of the tool is adjustable, the locking mechanism is such that adjustment cannot be accomplished rapidly. Moreover, the configuration of the aperture through which the instrument tip protrudes limits the number of orientations available.
U.S. Pat. No. 1,412,130 discloses a dental "scaler" comprising two hemispherical sections, each having a tapered end which is inserted into a hollow tube serving as the instrument body. The tapered ends are connected to a threaded rod running the length of the tube. The ball-end of a tool is inserted within the hemispherical sections. When the threaded rod is tightened, the tapered ends of the hemispherical sections are drawn into the tube, thereby causing the hemispherical sections to firmly grasp the ball-end placed therein. While this dental instrument also allows the orientation of the instrument tip of the tool to be adjusted, the locking mechanism is such that the adjustment is time consuming. Also, the clamping force on the ball-end is proportional to the degree to which the threaded rod is tightened. This is not desirable, since this procedure introduces uncertainty as to the strength in which the instrument tip is being held.
A dental instrument presently on the market and based on the concept of locking the tool by a screw-type mechanism is the "Zekyra," sold by Clinician's Choice.TM. Dental Products, Inc., of New Milford, Conn. The instrument comes with "protector tips" (i.e., tools) which are adjustable and locked into place relative to an instrument body, using a screw-type (i.e., threaded) locking mechanism.
In addition to dental devices, there are prior art patents which disclose devices for holding a tool having a ball-end. For example, U.S. Pat. No. 778,977 discloses a coupling device (a "Pitman coupling") comprising two arms each having hemispherical sections at their respective ends, wherein one of the arms is fixed to a body portion, while the other arm pivots about a pivot pin relative to the body portion. The pivotable arm is wedge-shaped at the end opposite the hemispherical section. A spring-loaded take-up wedge fits snugly against and pushes on the wedge-shaped end of the pivotable arm, thereby causing the hemispherical sections to grasp a ball-end placed therein. Unfortunately, this design also is such that the adjustment of the instrument tip attached to the ball-end cannot be achieved rapidly. Also, the coupling disclosed is not particularly well-suited for a dental instrument, since it is mechanically complex and appears to be incapable of readily providing enough force to hold the ball-end sufficiently tightly for dental applications.
U.S. Pat. No. 4,620,813 discloses a position-retaining mechanism having two hemispherical sections at the end of respective arms, each having a regular pattern of protrusions on their inner surfaces, and a ball-end having complimentary recesses, wherein the ball-end fits between the two hemispherical sections. The arms are pivotable about a pivot point and the ball-end is held snugly between the hemispherical sections by a spring which forces the arms apart, thereby forcing the hemispherical sections together. However, this position retaining mechanism is not particularly well-suited for a dental instrument, since the spring-type locking device would likely not provide sufficient clamping strength to hold the ball-end fixed while performing dental procedures. In addition, the number of orientations of an instrument tip attached to the ball-end would be limited. Moreover, the mechanism appears rather complicated to fabricate.